No glacial-interglacial cycle in the ice volume simulated under a constantastronomical forcing and a variable CO2

The relative impact of the CO2 concentration on climate-over the last 200 k yr is investigated here using the Louvain-la-Neuve 2-dimension Northern Hem isphere (LLN 2-D NH) climate model forced by different constant insolations and the variable CO2 concentration reconstructed from the Vostok ice-core record. Under such conditions the 100-kyr cycle in-the Northern Hemisphere ice volume cannot be reproduced. Either a warm orbit prevents the ice sheet s from forming-or a present-day and colder orbits do not allow them tol:mel t:after being formed. The global hemispheric temperature,, however, continu es to respond directly to the atmospheric CO2-concentration changes.